The overall objective of this project is to explore and develop new means of controlling caries by investigating methods whereby the transport of mineral out of tooth structures can be interfered with. To do this, polymer or polymer-forming formulations are to be developed to deposit materials inside early, subsurface, lesions. The polymer systems to be investigated are those which can be expected to operate as barriers against acid intrusion and/or by releasing fluoride into the local environment in the vicinity of lesions. Three different polymer systems are being studied: substituted-amine fluoride monomers, monomers with phosphonate substituents, and preformed polymers containing phosphonate and/or substituted-amine fluoride groups. Several amine-fluoride-containing monomers have been synthesized and were found to be capable of rapid homopolymerization at room temperature from either aqueous or alcoholic solutions. They are also readily crosslinked and copolymerized. This reduces their swelling in water, but swelling is still a problem. The fluoride salts of the various polymers release fluoride of HF by ion-exchange with electrolyte solutions (simulating oral fluids) at rates of 0.2 to 0.8 ppm/hr per gram of polymer. When applied to subsurface demineralized zones in extracted teeth, similar release rates are observed using either a preformed polymer deposited out of solution, or using monomers which are polymerized after being taken up by the lesions. Continuous release for up to one week has been observed. During the coming year further work will be conducted in order to develop oral-compatible, fluroide-exchanging, polymer systems which will be resistant to swelling. Work will also be continued in developing barrier-forming polymer systems to limit the intrusion of decay-causing materials into enamel defects and into lesions at an early, incipient, stage.